'M i c r ó ^ 662' c ö 'p ^c a-1 * Es’sbAY«.
prived of the bark; becaafe they have rays of the fame fubftance
within, which anfwer the. pürpöïfe,.sand this in a degree anfwering
to the nature of their life.
The bark appears to be'formed,'firft, o f lèngitudinal fibres,
which Duhamel confiders as --fo many lymphatic- veflels; feccmd-
ly, by a kind o f a filmy éelkïlar-tiflue-, -which have bfeea «onfidcr-
- ed as a kind of bladders by fome, or as parenchymous by'others;
thirdly, of thevafa propria interiora, or interior juice veflels.
The longitudinal fibres are difoofed in ftrata, which lie one
over the other?- In that1 {Ifatuitf -which is next 'thé rind; or rather
the Cellular coat, we perceiVé a nét o f longitudinal ‘fibres, the
mefhes o f which are large and èafily -diftiriguiffiéd, : particularly
when the cellular tiflile that fills up the interftices is-removed. T o
do this, the branches Ihould hé macerated for a confidcrable
time; fome require to be kept in this Hate for years. It will
then be eafy to feparate firflPthe- rind], their the Cellular coating,
and afterwards this pulpy matter. -It may fomfetimes be ealily re moved
after the branches have been boiled:* -) 1
- The móft exterior ftratüm, when examinedhythertaked eye»
Teems to be formed o f fimplè fibre's,' Which graft, - folder, or
-anaftomofe one with the other ; but when examined by,a micro-
fcópe, each of thefe fibres will be found to be a bundle of
-filaments, which may be eafi-lv feparatcd from each-other.
Grew fays, that each filamént, like1 thé' -nerves in animals,
confifts o f twenty or thirty fma'Il -contiguous- tubes, which run
uniformly from the extremity of the root, without fending off any
■ ‘ branches,
branches, or buffering any change in their lize and fhape. Hence
the bark may be tore or divided lengthways, with greater eafe
than in an horizontal direftion ; when macerated, they are capable
o f a Very great degree' of fubdivifion.
The filaments of a cortical veffel are to be looked on (agreeable
to what we have already obfer.ved) as fo many little bundles ■
placed near together, and at firft growing parallel to each other ;
but foon quitting this direction, the filaments o f one fafcicle parting
from that to which they originally belonged, and inclining
more or lefs obliquely towards another, fometimes uniting with
it, .at others: bending backwardsr.and uniting again with that from
-whichdt proceeded,- oti.with fome one that it irieets. with; In-this
maimer new.fafcicles.are often formed, while other parcels, are
increafed or diminilhed by the:additions-of new filaments; by-
this means,. a kind of irregular net is formed, and the fibres proceed
in a ferpentine line from the top to the bottom o f the tree..
The thicknefs o f the hark : is entirely formed of ftrata of thefe
longitudinal fibres;. which lie one over the. other ; each of thefe
ftrata is fimilar .to the exterior one, . only the. mefhes are fmaller,
-dndtth-ei fibres; fineiy1 in proportion ‘as they- ■ are more interio'r, in-
fomuch that, at laff: thd-mefhés are-almoft annihilated,, and th e -
fibres, Teem, to lie quite1 parallel ito-each other.-
. There; are fome,tries, however, where thfi-meffies are notvilible,-.
and. ini iwhichr,the fibres die :quite in a .lirait direftion, , There are ■
many other ciriumftances, in , which they vary- in, different trees ;
in fome thé mefhes of each ftràtum correfpond with each other,,
i g /. . Qjjj , ; ; ■ , diminilh--